The Ospreys had spent the week on the defensive after the latest mishap to befall their most celebrated player but responded with their biggest-ever Heineken Cup victory as Ulster failed to make it to the knockout stage for the eighth season in a row since winning the tournament.

The injured Gavin Henson may have been absent but the Ospreys but showed no signs of missing him in the early stages. Sonny Parker, covering Henson's position at inside-centre, scored the game's opening try on four minutes after Lee Byrne had split the defence in a routine move.

Henson will not be seen by the club until the new year because of a left-hand injury but they continued yesterday to deny that the broken bone had been caused by his part in drinking games with friends on the train back from Harlequins last Sunday. It was pointed out that Henson had been named in the original squad on Tuesday for last night's game because he was desperately keen to play, even though it was claimed he had been treated for the injury immediately after the win at The Stoop.

Ulster, fielding 10 of the side who clinched the Celtic League title here less than two years ago, found it hard to figure out the Ospreys' on-field approach and were 15 points down in the opening quarter. The 1999 Heineken Cup winners, without a head coach for at least another month, offered marginally more resistance than the Ospreys would have expected in an unopposed training session.

First tackles were broken at will and when Shane Williams jinked through the defence from a scrum on halfway, he was so surprised to encounter no obstacles on his way to the Ulster 25 that he lost track of his support runners and threw the ball forward.

Justin Marshall, however, clung on to score after sniping from a ruck and Bryn Cunningham's flimsily attempted tackle summed up Ulster's season. Yet the Ospreys led only 15-3 at the break despite dominating possession, but it was mainly due to a tendency to over-elaborate.

The Ospreys were shaken and stirred by the interval team-talk from head coach, Lyn Jones, and within seven minutes had claimed a try bonus point , when the second row Alun Wyn Jones and the No 8 Filo Tiatia profited from regulation, rather than fancy, handling and passing. Then it was almost as if a light had been switched off as Ulster began a period of possession that led to Isaac Boss crossing for an unlikely try.

The Scotland wings Nikki Walker and Simon Danielli exchanged tries before Byrne and Walker completed the scoring to leave the Ospreys still hunting Gloucester.